In rotary regenerative heat exchange apparatus a mass of heat absorbent element commonly comprised of packed element plates is first positioned in a hot gas passageway to absorb heat from hot gases passing therethrough. After the plates become heated by the hot gases they are moved to a passageway for a cooler fluid where the then hot plates transmit their heat to cooler air or other gas passing therethrough.
The heat absorbent material is carried in a rotor that rotates between the hot and cool fluids, while a fixed housing including sector plates at opposite ends of the rotor is adapted to surround the rotor. To prevent mingling of the hot and cold fluids, the end edges of the rotor are provided with flexible sealing members that rub against the adjacent surface of the rotor housing and resiliently accommodate a limited degree of "turndown" or other distortion caused by mechanical loading and thermal deformation of the rotor.
To permit turning the rotor freely about its axis, certain minimum clearance space between the rotor and adjacent rotor housing is required, however, excessive clearance is to be avoided because it will dictate excessive leakage. However, under conditions marked by a rapid increase of temperature that is accompanied by excessive expansion of the rotor and of the rotor housing, excessive leakage may develop and a lowered effectiveness may result.
The expansion of the rotor and adjacent rotor housing assumes the greatest proportions directly adjacent the inlet for the hot fluid where an increase of temperature is maximum. An arrangement that compensates for a loss of sealing effectiveness at this, the "hot" end of a rotor, is shown by U.S. Pat. No. 3,786,868 where a plane sector plate is pivoted about a fulcrum carried by the housing. Although such an arrangement is partially effective, excessive fluid leakage between the sector plate and the rotor still continues because the sector plate distorts as a plane while the rotor distorts in a dished configuration.